Update public docs: Safeguard against using latest

[cristiklein]

We recently added a safeguard to Compliant Kubernetes to disallow container images with certain tags that do not belong in production, by default latest.

This task consist in creating user-facing documentation for this safeguard. A good template to follow is:

# «Benefit, briefly»: «How that benefit is technically achieved, briefly»

!!!note
    This section helps you implement ISO 27001, specifically:
    «List of relevant ISO control, change management is most relevant here»

«One sentence for the problem. One sentence for the solution in Compliant Kubernetes. One sentence for the benefit to the application developer.»

## How to solve: «Error produced by Gatekeeper/OPA policy»

You may encounter the following issue:

«Copy-paste of relevant terminal example»

This means that «plain English translation».

To fix this, you have the following options:

«List of options»

## Further Reading

«Relevant upstream documentation»

Check other user-facing safeguard pages for inspiration.

Acceptance criteria:

• elastisys.io has a new safeguard following the template